Ethernet is a family of frame-based computer networking technologies implemented at the link layer of the Internet Protocol (IP) suite model. The Ethernet frames implemented in this model include fields describing the Media Access Control (MAC) addresses of devices utilizing the network within which the protocol is implemented. Example fields include a destination MAC address field, a source MAC address field, an Ether Type field, a load field, and other fields. These fields are outlined, for example, in the Institute of Electrical and Electronics Engineers (IEEE) 802.3 standard.
Networks using Ethernet typically broadcast (e.g., flood) messages across a spanning tree operatively connecting the devices that are part of this network. These devices include switches (e.g., layer 1-2 devices), routers (e.g., layer 1-3 devices), and host devices. Operatively connected, as used herein, is a logical or physical connection. A connection between any two adjacent devices is a link.
Networks using Ethernet may also unicast messages along links that operatively connect devices in the network. For example, when a device “X” receives a message from a device “Y” on a link, an entry in a forwarding table is created so that all subsequent messages received by device “X” destined for device “Y” are sent along the same link. Using this method, device “X” can be taught a link in a path that ultimately leads to device “Y.” This form of teaching is symmetric (referenced herein as symmetric teaching) in nature for the path from device “Y” to device “X” is effectively retraced to deliver a message from device “X” to the device “Y.”